In an image forming apparatus, sheets such as paper need to be fed sheet by sheet to an image forming unit. Accordingly, for example, an image forming apparatus is known that is provided with a separation mechanism including a separation roller and a frictional resistance body, such as a separation pad or the like, that separates a plurality of sheets from each other and that feeds the sheets sheet by sheet to an image forming unit.
The separation roller rotates while in contact with the sheet to give transporting force to the sheet. The frictional resistance body is disposed at a position opposing the separation roller and gives frictional resistance to the sheet. Accordingly, only the sheet that is in contact with the separation roller is fed and the other sheets are stopped by frictional resistance without being fed.
A roller mechanism for transporting a sheet typically gives transporting force to the sheet by pinching the sheet from both the front and back side; accordingly, the roller mechanism is provided with a first transport roller and a second transport roller. The first transport roller and the second transport roller extend entirely across the sheet transport path in the width direction.
The second transport roller is capable of being displaced in a direction moving away and moving towards the first transport roller. Furthermore, in order to increase a contact pressure (hereinafter, also referred to as a nip pressure) between the first transport roller and the second transport roller, two end sides of the second transport roller in the shaft direction are pressed towards the first transport roller side with pressing members such as springs.
However, since the pressing members press the two end sides of the second transport roller in the shaft direction, the nip pressure becomes smaller the nearer to the middle of the second transport roller in the shaft direction. Accordingly, when a sheet with a small width is transported, the sheet cannot be nipped with a high nip pressure and, further, frictional resistance from the frictional resistance body acts on the sheet. Therefore, when a sheet with a small width is transported, transport failures such as the sheet being transported out of position at an angle easily occur.